System and method for treatment of gases with reducing agents generated using steam reforming of diesel fuel

ABSTRACT

Systems and methods for treatment of a heated exhaust gas including hydrocarbons are provided. A method includes providing a first gas including a gaseous mixture of vaporized diesel fuel and steam and treating the first gas using at least one corona discharge including a combination of streamers to transform the first gas into a second gas including volatile partially oxidized hydrocarbons (PO—HC) and hydrogen gas (H 2 ), the combination of streamers including primarily surface streamers. The method also includes extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas and directing a combination of the third gas and the exhaust gas into a nitrogen oxides (NOx) reduction reactor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT patent application No. PCT/US2012/024249, filed Feb. 8, 2012, which claims priority to U.S. Provisional Patent Application Ser. No. 61/440,664, filed Feb. 8, 2011, both of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to systems for treating gases including pollutants. More specifically, the invention relates to systems and methods for treating gases including pollutants using reducing agents generated via steam reforming of diesel fuel with a corona discharge plasma reactor.

2. Background

Diesel exhaust contains pollutants like CO, hydrocarbons (HC), nitrogen oxides (NOx), and soot particles that need to be removed before it can be safely released into the environment. In general, about ninety percent of the nitrogen oxides exist as nitrogen monoxide (NO) which is typically difficult to destroy. The remaining nitrogen oxides are typically composed of nitrogen dioxide (NO₂) that can be destroyed by hydrocarbon selective catalytic reduction (H-SCR) or by urea selective catalytic reduction U-SCR. In general, several technologies based on oxidation catalysts and diesel particulate filters (DPF) for removal of CO, HC, and soot particles are available. However, technologies for destruction/removal of NOx are still being developed.

SUMMARY

The various embodiments are directed to systems and methods for treatment of gases. In a first embodiment, a method for treatment of a heated exhaust gas including hydrocarbons is provided. The method includes providing a first gas including a gaseous mixture of vaporized diesel fuel and steam and treating the first gas using at least one corona discharge including a combination of streamers to transform the first gas into a second gas including volatile partially oxidized hydrocarbons (PO—HC) and hydrogen gas (H₂), the combination of streamers including primarily surface streamers. The method also includes extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas and directing a combination of the third gas and the exhaust gas into a nitrogen oxides (NOx) reduction reactor. The method can also include heating the discharge chambers using the heated exhaust gas.

In the method, the step of providing can include directing a liquid mixture of liquid diesel fuel and water into a heat exchanger and applying the heated exhaust gas to the heat exchanger to vaporize the liquid mixture and produce the first gas.

The step of treating can include providing one or more discharge chambers defined by a plurality of dielectric sections, each of the discharge chambers including at one or more sets of first and second electrodes for producing electric fields in the discharge chambers, the plurality of dielectric sections and the sets of first and second electrodes arranged to define a volume in each of the discharge chambers that inhibits the formation of volume-streamers, and the discharge chambers being configured to prevent pulsed electric fields generated in adjacent ones of the discharge chambers from substantially interacting. The step of treating can also include directing the first gas into the discharge chambers, generating the corona discharge in the discharge chambers using a pulsed electric field generated by each of the sets of the first and second electrodes in the discharge chambers, and releasing the second gas from the discharge chambers.

The step of extracting can include directing the second gas into a heat exchanger and cooling the second gas in the heat exchanger to condense water and liquid diesel fuel from the second gas. The step of providing can include forming at least a portion of the first gas using the condensed water and the condensed liquid diesel fuel.

In a second embodiment of the invention, an exhaust system is provided. The system can include a nitrogen oxides (NOx) removal reactor, an inlet portion configured for receiving a heated exhaust gas including hydrocarbons and directing the heated exhaust gas into the catalytic reactor, and a reformer system heated by the heater exhaust gas. The reformer system can include a gas treatment device for treating a first gas including a mixture of vaporized diesel fuel and steam using at least one corona discharge including a combination of streamers to transform the first gas into a second gas including volatile partially oxidized hydrocarbons (PO—HC) and hydrogen (H₂), the combination of streamers including primarily surface streamers and a recycling system for extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas and directing the third gas into the inlet portion. In some configurations, the heat exchanger is disposed in the inlet portion. Further, the NOx removal reactor includes at least one of a hydrocarbon selective catalytic reduction (H-SCR) reactor and a NOx adsorbent.

The reformer system can include a first heat exchanger for receiving a liquid mixture of liquid diesel fuel and water and generating the first gas, where the first heat exchanger is configured for generating the first gas by vaporizing the liquid mixture using the heated exhaust gas. The system can also include a water source for providing the water to the first heat exchanger and a fuel source for providing the liquid diesel fuel to the first heat exchanger.

The recycling system can include a second heat exchanger coupled to an outlet of the plasma reactor and configured for producing the third gas by condensing water and liquid diesel fuel from the second gas, a recycle supply line for directing the condensed water and the condensed liquid diesel fuel from the second heat exchanger to the first heat exchanger, and a reactant supply line for directing the third gas from the second heat exchanger to the inlet portion.

The gas treatment device can include one or more discharge chambers defined by a plurality of dielectric sections, each of the discharge chambers including at one or more sets of first and second electrodes for producing electric fields in the discharge chambers, where the plurality of dielectric sections and the sets of first and second electrodes are arranged to define a volume in each of the discharge chambers that inhibits the formation of volume-streamers, and where the discharge chambers being configured to prevent pulsed electric fields generated in adjacent ones of the discharge chambers from substantially interacting. In some cases, a heating the discharge chambers can be provided using the heated exhaust gas. Further, the discharge chambers can be disposed in the inlet portion.

In third embodiment of the invention, a diesel fuel powered system is provided. The system includes a diesel fuel engine including an exhaust outlet for releasing exhaust gas, a hydrocarbon selective catalytic reduction (H-SCR) reactor, an inlet portion configured for directing the exhaust gas from the exhaust outlet to the H-SCR reactor, and a gas treatment device at least partially disposed in the inlet portion, the gas treatment device configured for treating a first gas including a mixture of vaporized diesel fuel and steam using at least one corona discharge including a combination of streamers to transform the first gas into a second gas including volatile partially oxidized hydrocarbons (PO—HC) and hydrogen (H₂), the combination of streamers including primarily surface streamers. The system also includes a first heat exchanger at least partially disposed in the inlet portion and configured for generating the first gas from water and liquid diesel fuel using a heat of the exhaust outlet and a recycling system coupled to the plasma reactor to receive the second gas, the recycling system configured for extracting liquid diesel fuel and water from the second gas to form a third gas, directing the third gas into the inlet portion, and directing the extracted liquid diesel fuel and the extracted water into the first heat exchanger. The first heat exchanger can be disposed in the inlet portion.

The system can also include a water source for providing the water to the first heat exchanger and a fuel source for providing the liquid diesel fuel to the first heat exchanger and the diesel fuel engine.

The recycling system can include a second heat exchanger coupled to an outlet of the plasma reactor and configured for producing the third gas by condensing water and liquid diesel fuel from the second gas, a recycle supply line for directing the condensed water and the condensed liquid diesel fuel from the second heat exchanger to the first heat exchanger, and a reactant supply line for directing the third gas from the second heat exchanger to the inlet portion.

The gas treatment device can include one or more discharge chambers defined by a plurality of dielectric sections, each of the discharge chambers including at one or more sets of first and second electrodes for producing electric fields in the discharge chambers, where the plurality of dielectric sections and the sets of first and second electrodes are arranged to define a volume in each of the discharge chambers that inhibits the formation of volume-streamers, and where the discharge chambers being configured to prevent pulsed electric fields generated in adjacent ones of the discharge chambers from substantially interacting. The discharge chambers can be disposed in the inlet portion.

In a fourth embodiment of the invention, an exhaust system is provided. The system includes a nitrogen oxides (NOx) removal reactor, an inlet portion configured for receiving a heated exhaust gas including hydrocarbons and directing the heated exhaust gas into the catalytic reactor, and a reformer system heated by the heater exhaust gas in the inlet portion, the reformer system including a plasma reactor for treating a first gas including a mixture of vaporized diesel fuel and steam using at least one corona discharge including volume streamer and surface streamers to transform the first gas into a second gas including volatile partially oxidized hydrocarbons (PO—HC) and hydrogen (H₂), and a recycling system for extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas and for directing the third gas into the inlet portion.

In the system, the plasma reactor includes a plurality of dielectric sections defining two or more discharge chambers for treating the first gas, first and second electrodes disposed in each of the discharge chambers, and electrically conductive shield portions positioned between adjacent ones of the discharge chambers. Further, the plurality of dielectric sections and the first and second electrodes are arranged so that a greater portion of overall energy density within the discharge chambers is due to the surface-streamers.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show top and side views, respectively, of a surface-streamer based plasma reactor that is useful for describing the various embodiments of the invention;

FIG. 2 is a partial cross-section diagram of a first exemplary configuration for a gas treatment device in accordance with an embodiment of the invention;

FIGS. 3A and 3B are partially exploded and assembled view, respectively, of one exemplary configuration for a gas treatment device in accordance with an embodiment of the invention;

FIG. 4 is a partial cross-section diagram of another exemplary configuration for a gas treatment device in accordance with an embodiment of the invention;

FIG. 5 is a schematic of an exemplary diesel fuel powered system configured in accordance with an embodiment

FIG. 6 illustrates a system including a gas treatment device, configured in accordance with an embodiment of the invention, and supporting electrical circuitry.

FIG. 7 is a detailed block diagram of a computing device which can be implemented as a control system.

FIG. 8 is a bar chart showing a comparison of energy cost for partial oxidation of organic pollutants from air and reduction of nitric oxide from nitrogen in pulsed corona discharges in air (conventional plasma reactors) and the sliding discharge reactor.

DETAILED DESCRIPTION

The invention is described with reference to the attached figures, wherein like reference numerals are used throughout the figures to designate similar or equivalent elements. The figures are not drawn to scale and they are provided merely to illustrate the instant invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the invention. The invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the invention.

As described above, a principal concern in the treatment of diesel engine exhaust and other fossil fuel engine exhaust is the destruction/removal of NOx, and particularly the destruction of NO. One method of dealing with NO is to oxidize NO into NO₂ using oxidation catalysts and thereafter using H-SCR or U-SCR to eliminate the NO₂. However, such an approach generally requires on-board supply of the reducing agents, i.e., hydrocarbons, hydrogen or urea. In the case of a diesel fuel system, diesel fuel itself comprises of hydrocarbons, but these hydrocarbons are generally long chain hydrocarbons and aromatic compounds that are not effective reducing agents in H-SCR processes. A solution is to reform the diesel fuel to obtain Hydrogen (H₂) and partially oxidized hydrocarbons (PO—HC), which are effective reducing agents for the H-SCR process.

One option for reforming fuels is to use plasma treatments. Plasma, i.e., a partially ionized gas, can be formed by high voltage electrical discharges. The plasma can be thermal where ions as well as neutral particles are close to thermal equilibrium or it can be non-thermal where electrons are selectively heated while the heavier ions and neutral particles remain close to room temperature. For example, high voltage pulse of short rise time and short duration are applied between the electrodes in pulsed corona discharges. Electrons, being light weight, accelerate to high energy state while the heavier ions do not have sufficient time to accelerate to high energy states during the voltage pulse. The high energy electrons ultimately collide with ambient gas molecule and cause dissociation, excitation or ionization. These processes produce chemically active species, such as N, O, O₃, etc. The high energy electrons and chemically active species can react with and transform the hydrocarbon molecules. However, conventional thermal and non-thermal plasma reactors typically consume large amounts of energy. Further, to treat a large volume of gas efficiently, the non-thermal plasma reactors typically occupy a substantially large volume. As a result, assembling a lightweight, compact exhaust system that uses steam reforming based on a plasma reactor is typically difficult using conventional non-thermal plasma reactor configurations.

Accordingly, the various embodiments provide new exhaust systems and methods utilizing steam reforming based on high-efficiency, compact surface-plasma reactors using pulsed corona discharges. Such reactors generally consume significantly less energy as compared to conventional volume-plasma reactors for conversions of the hydrocarbons. In particular, a plasma reactor configuration is provided in the exhaust system that includes a stacked arrangement of multiple discharge chambers that can be operated in parallel. The compact size of these surface-plasma reactors is advantageous, particularly for applications in vehicles. The operation and configuration of such a plasma reactor is described below with respect to FIGS. 1-4.

FIGS. 1A and 1B show top and side views, respectively, of a plasma reactor 100, configured for encouraging primarily surface-streamers, which is useful for describing the invention. As shown in FIGS. 1A and 1B, the reactor 100 is an enclosure defining a discharge volume or chamber 102. The discharge chamber 102 is defined by a collection of surfaces. For example, as shown in FIGS. 1A and 1B, the discharge chamber is defined by opposing upper and lower dielectric portions or surfaces 104, opposing dielectric end portions 106, and lateral or side portions 108.

The reactor 100 can also include an inlet a 114 and an outlet 116 for directing gas in and out, respectively, of the discharge chamber 102. In the configuration illustrated in FIGS. 1A-1B, the reactor 100 is shown as including a single inlet 114 and a single outlet 116 positioned at end portions 106. However, the number and placement of inlets and outlets can vary for reactor 100.

The discharge chamber 102 further includes electrodes 110 and 112 for producing plasma in the discharge chamber 102 using a short high voltage pulse, such as pulses less than 1, 10, or 100 microseconds. Use of a short pulse prevents arcing. As shown in FIG. 1A, the reactor 100 includes an anode electrode 110. In FIG. 1, an anode electrode 110 is shown as a wire inserted across discharge chamber 102. Electrode 110 may also be a threaded rod, sharp edge, or any other localizing configuration of electrode capable of producing streamers, as is known to those in the field and may be appropriate for the application.

Reactor 100 also includes one or more cathode electrodes 112. In the configuration illustrated in FIGS. 1A and 1B, the second electrode is shown as a solid electrical conductor disposed on an inner surface of lateral side portions 108. However, lateral side portions 108 and electrodes 112 can be integrally formed. Further, the cathode electrodes 112 can also be in the form of a wire mesh, a plate, a wire, or other conductive electrode configuration known in the art. Additionally, the lateral side portions 108 and the electrodes 112 can be configured to permit the flow of gas into and out of gas discharge chamber 102 through cathode electrodes 112. For example, by positioning from gas inlet 114 into reactor 100 along lateral side portions 108 and sizing or configuring cathode electrodes 112 to allow gases to flow through cathode electrodes 112 and into discharge chamber 102. After treatment, the gas exits through another of cathode electrodes 112 and side portion 108 by gas outlet 116.

As shown in FIGS. 1A-1B, reactor 100 shows a substantially wire-to-plate arrangement of electrodes 110 and 112. As shown in FIG. 1A, the anode electrode 110, in this case a wire, is located at equal distance to the two cathode electrodes 112. However, the various embodiments of the invention are not limited to this exemplary configuration for a reactor. For example, a position of anode electrode 110 can vary and need not be exactly equidistant between electrodes 112. Further, electrode 110 can be disposed on or near a first of dielectric portions 104. However, the various embodiments are not limited in this regard and the position of electrode 110 with respect to dielectric portions 104 can vary. That, is the electrode 110 can be either placed on or near either of dielectric portions 104, equidistant between the two surface 104, or any position in between, as long as the distance of the wire to the sheets is small enough such that surface streamers are primarily generated in the reactor 100.

Further, the various embodiments are not limited to wire-to-plate configurations. Thus, the anode and cathode electrodes can be arranged in a wire-to-wire configuration, a point-to-wire configuration, or a point-to-plate configuration, to name a few. Further, the roles of the electrodes in the various embodiments can be reversed. That is, electrode 110 and electrode 112 can be switched to provide a cathode and an anode, respectively.

In one exemplary configuration of reactor 100, it can be constructed using sheets or films consisting of glass, ceramic, or other high temperature resistant dielectric materials, as dielectric surfaces 104, a stainless steel wire of 150 micro-meter diameter as anode electrode 110, aluminum strips of 6 mm thickness as cathode electrodes 112. End portions 106 can also be formed using glass, ceramic, or other high temperature resistant dielectric materials. An example of a suitable high temperature dielectric material is MACOR®, developed and sold by Corning Incorporated of New York, N.Y. However, the various embodiments are not limited to the exemplary materials described above. For example, the electrodes 110 and 112 can be fabricated from any electrically conducting or semi-conducting materials. However, metals, such as stainless steel, copper, silver, tungsten, or alloys thereof would provide superior performance.

Exemplary dimensions for reactors using such materials and the typically achievable energy per pulse are listed in Table 1.

TABLE 1 Dimensions of discharge spaces of three reactors employed. Length Width Height Energy per pulse Reactor Cm cm Cm J ± 1σ 1 8 10 0.2 0.0085 ± 0.002  2 30 9 0.2 0.035 ± 0.008 3 30 9 1.4 0.034 ± 0.007 4 15 ID**: 4.5 — 0.10 ± 0.01 In Table 1, Reactor 4 is a conventional coaxial reactor (not shown) with the discharge gap defined by the diameter of the cylinder and operating in a volume-streamer mode. Reactors 1, 2, and 3 are reactors configured in accordance with FIGS. 1A and 1B and operating in surface-streamer mode. The dimensions and achievable energy per pulse for Reactor 4 is shown for purposes of comparison.

In addition to the configuration described above, the ends of the first electrodes 110 within the discharge chamber 102 can be insulated to eliminate surface-streamer at the end portions 106. For example, a 2.5 cm part each end of the electrodes can be used to insulate electrodes 110 and 112 to eliminate surface-streamers at the end fittings. Accordingly, the effective length of the electrodes would be 5 cm less than that listed above.

Those skilled in the art will recognize that the configuration of the discharge chamber, the gas, and the electrodes will vary the effective length at which the formation of streamers is effectively constrained so that surface-streamers play a primary role in energy density. For example, spacing between the dielectric surfaces 104 may be used to reduce the dimensions of discharge chamber 102 so as to constrain the formation of volume-streamers, given the electrode configuration described above. In the embodiment of FIG. 1, a distance of 10 mm between dielectric surfaces 104 was shown to be effective to significantly reduce or eliminate the formation of volume-streamers. Smaller distances are preferable in that they increase the role of surface-streamers with a corresponding increase in energy density. The design of a plasma reactor with a discharge chamber, in which surface-streamers are predominant, is described in U.S. Pat. No. 7,298,092 to Malik et al., issued Nov. 20, 2007, the contents of which are hereby incorporated in their entirety.

Although the plasma reactors described above can generate a sufficient volume of surface-streamers to provide effective treatment, combining several of these reactors into a small space can be difficult. For example, where two of the reactors shown in FIGS. 1A and 1B are placed directly on top of each other or constructed using a common one of dielectric portions 104 and operated in parallel using a common power supply, plasma will typically be observed in one chamber only. This is believed to be due to positive surface charge that the surface plasma leaves on the dielectric surface in contact with the plasma. This charge on one side of the dielectric induces an opposite charge on the other side, which appears to change or interact with the electric field distribution in the adjacent discharge chamber. As a result, this interaction results in an electric field distribution which is not favorable to plasma formation. In other words, when two surface-plasma reactors are operated adjacent to each other, they can become electrically coupled with each other. Normally, this can occur is the electrical field of one of the reactors is sufficiently strong causing accumulation of charges on an opposing dielectric surface. As a result, plasma formation will occur in one reactor only, decreasing treatment efficiency. As a result, combining a number of such reactors in a small space will not result in improved treatment of gases.

Accordingly, in the various embodiments, the exhaust system is configured to include a reforming system to include adjacent surface-plasma reactors with shield portions to prevent the inducement of opposite charges in one reactor due to surface plasma discharge in an adjacent chamber. Thus, a reforming system for an exhaust system can be formed by scaling up a surface-plasma reactor by operating multiple reactors in parallel or series and positioned adjacent to each other, by separating them with a shield portion held at a reference voltage.

FIG. 2 is a partial cross-section diagram of a first exemplary configuration for a gas treatment device 200 in accordance with an embodiment of the invention. In particular, FIG. 2 is a stacked arrangement of two of reactor 100 (reactors 100A and 100B), where the cross section shown in FIG. 2 is a portion of the cross-section along cutline 2-2 in FIG. 1 for each of reactors 100A and 100B. That is, each of reactors 100A and 100B is configured substantially similar to reactor 100 in FIG. 1.

The partial cross-section of device 200 shows the top and bottom dielectric portions 104A and 104B for each of reactor 100A and 100B, respectively. In device 200, the decoupling between reactors 100A and 100B is provided by introducing an electrically conductive shield portion 202 between the reactors 100A and 100B. Particularly, the shield portion 202 is disposed between the contacting ones of dielectric portions 104A and 104B. Thus, this shield portion 202 can decouple the two reactors 100A and 100B by providing a conducting medium which prevents the induction of charges on the dielectric which is part of the neighboring reactor.

In operation, the shield portion 202 is connected to a reference voltage that is the same or lower than that of the electrodes in each of reactor 100A and 100B. For example, the shield portion 202 can be coupled to ground. As a result, the electric field generated in first of discharge chambers 102A is effectively blocked from entering a second of discharge chambers 102B. The electric charge induced on the dielectric surface is transported by the conductive shield. Accordingly, the lack of induced charges results in the ability to generate plasma in both adjoining discharge chambers 102A and 102B.

In some embodiments of the invention, the shield portion 202 and the electrodes in reactors 100A and 100B can be separately biased, as described above. However, in some configurations, the shield portion 202 and the cathode electrodes in reactors 100A and 100B can be biased and/or electrically connected. Such a configuration simplifies the circuitry required for operating device 200. That is, separate circuits are not required for biasing shield portion 202 and the cathode electrodes in reactors 100A and 100B. Further, since these portions are substantially adjacent to each other, a simpler wiring for these portions can be provided.

In the configuration shown in FIG. 2, two separate reactor chambers are shown, separated by the shield portion. However, the various embodiments of the invention are not limited in this regard. In other embodiments, the reactors can share a common dielectric portion, where the dielectric portion includes a shield portion embedded or otherwise integrally formed within the common dielectric portion.

Additionally, the shield portion can be formed in several ways. For example, in some embodiments of the invention, the shield portion can be formed using a sheet or foil of electrically conductive material. For example, the sheet or foil can consist of a metal or metal alloy. However, the various embodiments of the invention are not limited to shield portions consisting of metallic conductors. Rather, non-metallic conductors can also be used without limitation. Further, the various embodiments are not limited to solely a sheet-type or foil-type shield portions. In some configurations, a perforated sheet or foil can also be used to provide the shield portion. In yet other configurations, the electrically conductive materials of the shield portion can be arranged to form a mesh or screen. In still other configurations, a plurality of shield portions can be used, each coupled to a reference voltage.

Referring now to FIGS. 3A and 3B, there is shown one exemplary configuration of a gas treatment device 300, arranged in accordance with an embodiment of the invention. FIG. 3A is a partially exploded view of device 300. FIG. 3B is an assembled view of device 300. As shown in FIGS. 3A and 3B, device 300 includes a first reactor 302 and a second reactor 304. Each of reactors 302 and 304 includes a discharge chamber 306, defined by a stack of layers. In particular, the stack includes a first dielectric layer 308, a second dielectric layer 310, and a spacer layer 312 disposed between dielectric layers 308 and 310.

In the configuration shown in FIGS. 3A and 3B, the stack of layers 308-312 can be formed using layers or sheets of dielectric materials, as described above with respect to FIG. 1. However, the various embodiments of the invention are not limited in this regarding and any other dielectric materials can be used for forming layers 308-312. To define discharge chamber 306, layers 308-312 are configured to provide an enclosure. In particular, dielectric layers 308 and 310 are configured to be substantially solid to provide upper and lower surfaces of such an enclosure. The side surfaces of the enclosure are provided by the spacer layer 312. In particular, spacer layer 312 includes an opening for defining the discharge chamber 306 between layers 308 and 312. Accordingly, by adjusting the size of the opening in spacer layer 312 and the thickness of spacer layer 312, the volume of discharge chamber 306 can be varied. Accordingly, as described above, this opening size and thickness can be selected to adjust the amount of surface- and volume-streamers for the discharge chamber.

Gas flow into the discharge chamber 306 can be provided using an inlet 314 and an outlet 316. In FIGS. 3A and 3B, the inlet 314 and the outlet 316 are shown as being incorporated into first dielectric layer 308. However, the various embodiments of the invention are not limited in this regard. Rather inlet 314 and outlet 316 can be formed in any of layers 308-312. Further the inlet 314 and outlet 316 of each of reactors 302 and 304 can be coupled to provide each serial or parallel communication of gases between the reactors 302 and 304. Such a communication can be provided using conduit or tubing portions (not shown).

However, gas communication between the reactors 302 and 304 is not limited to using conduit or tubing portions. For example, as shown in FIGS. 3A and 3B, reactors 302 and 304 are in a stacked configuration, where a second dielectric layer 310 of reactor 302 faces a second dielectric layer 310 of reactor 304. Accordingly, the reactors 302 and 304 can be configured to allow gas communication via respective ones of dielectric layer 310. In particular, dielectric layer 310 in each of reactors 302 and 304 can include any arrangement of openings such that when reactors 302 and 304 are stacked on each other, the discharge chamber 306 of reactors 302 and 304 are in gas communication. Accordingly, the use of conduits can be limited for purposes of directing a gas in or out of device 300.

In reactors 302 and 304, plasma streamers in a corresponding discharge chamber 306 are formed via anode electrode 318 and cathode electrodes 320. Although electrodes 318 and 320 are referred to as anode and cathode electrodes, respectively, this is for illustrative purposes only. In the various embodiments of the invention, these roles can be reversed, as described above with respect to FIGS. 1A and 1B. As shown in FIG. 3A, cathode electrodes 320 are formed by providing an electrically conductive surfaces along two facing sides of discharge chamber 306. In particular, an electrically conductive material is disposed on portions of spacer 312, such that two facing and substantially parallel electrodes are formed within discharge chamber 306. Anode electrode 318 is then formed using a wire extending across the opening in spacer layer 312, as shown in FIG. 3A. In particular, the wire for anode electrode 318 is disposed in discharge chamber 306 so that it extends substantially parallel and between to the cathode electrodes 320 formed on spacer layer 312. Further, the wire is disposed in discharge chamber 306 to provide an electrode that is substantially equidistant from each of cathode electrodes 320. That is, in a substantially wire-to-plate relationship. However, other relationships can be used in the various embodiments of the invention, as described above with respect to FIGS. 1A and 1B.

Although FIG. 3 shows a wire for forming anode electrode 318, the various embodiments of the invention are not limited in this regard, as described above with respect to FIG. 1. In the various embodiments, the structure for anode electrode 318 can vary. Rather, any configuration that results in a greater electric field density at or near the anode electrode 318, as compared to cathode electrodes 320, can be used in the various embodiments of the invention. Accordingly, one or more pin-like or blade-like structures can also be provided to form anode electrode 318. Further, although the wire forming anode electrode 318 is shown as extending along the entire width or length of the opening in spacer layer 312, the various embodiments are not limited in this regard. In other configurations, a wire or blade-type structure for anode electrode 318 can extend only along a portion of the opening. In still other configurations, a series of wires, pin-type structures, or blade-type structures can be used over a portion or the entire length or width of the opening in spacer layer 312.

In operation, a voltage can be applied to anode electrode 318 via a portion of the wire forming anode electrode extending through spacer layer 312. However, alternatively or in addition to such a wire portion, spacer layer 312 or other portions of reactors 302 and 304 can be configured to include any type of connector structure for providing a voltage for anode electrode 318. Thus, such structures can be disposed on or extend through one or more portions of any of layers 308, 310, and 312. Similarly, a voltage can be applied to cathode electrodes 320 via a portion of the electrically conductive surfaces extending to outer surfaces of spacer layer 312. Thus, alternatively or in addition to such portions, spacer layer 312 or other portions of reactors 302 and 304 can be configured to include any type of connector structure for providing a voltage for cathode electrodes 320. Preferably, dielectric isolation can be provided between the anode electrode 318 for reactors 302 and 304. For example, as shown in FIGS. 3A and 3B, portions of dielectric layer 310 can extend along a length of anode outside the discharge chamber 306. Thus, such structures can also be disposed on or can also extend through one or more portions of any of layers 308, 310, and 312.

To provide decoupling between reactors 302 and 304, a shield portion for the device 300 can be formed by providing an electrically conductive portion between inner dielectric layers 310 and thereafter connecting this shield portion to a reference or ground voltage, as described above. However, as shown in FIGS. 3A and 3B, for each of reactors 302 and 304, a shield portion 322 is provided that is electrically connected to the cathode electrodes 320 of a corresponding one of reactors. Thus, a single voltage can be provided for the shield portion 322 and cathode electrodes 320 for the reactors 302 and 304 in device 300. Thus reduces requirements and complexity for a circuit providing power to device 300.

Additionally, to further reduce wiring requirements for device 300, the shield portion 322 and cathode portions 320 can be configured in each of reactors 302 and 304 so that the assembling of device 300 automatically electrically connects these portions in reactors 302 and 304. For example, as shown in FIG. 3A, shield portion 322 is disposed on an outer surface of second dielectric layer 310 in each of reactors 302 and 304. Thus, when device 310 is assembled as shown in FIG. 3B, the shield portion 322 of reactor 302 is placed in physical and electrical contact with the shield portion 322 of reactor 304. Accordingly, if a reference of ground voltage is applied to shield portion 322 or either of cathode electrodes 320 in reactor 302 or reactor 304, all of these portions in both of reactors 302 and 304 are biased to the same reference voltage. In the some embodiments of the invention, the reference voltage can be a ground potential. However, the invention is not limited in this regard and the reference voltage can be any voltage suitable for electrodes 320. That is, at least the voltage difference provided between electrodes 318 and 320 should be provided between electrode 318 and shield portion 322.

In the various embodiments, the connection between shield portion 322 and cathode electrodes 320 can be provided in various ways. In some configurations, electrically conductive wires and/or any other types of electrically conductive elements or structures can be used to provide the connection. In the configuration shown in FIGS. 3A and 3B, this connection is provided by forming shield portion 322 and cathode electrodes 320 using a continuous electrically conductive portion, such as an electrically conductive foil or sheet. In such configurations, foil or sheet can be configured as follows. First, a foil or sheet can be provided, with first and second ends that extend along the outer surface of second dielectric layer 310 that corresponds to at least discharge chamber 306. The first end of the foil or sheet can be wrapped around a first side portion of spacer layer 312 and the second end can be wrapped around a second side portion of spacer layer 312 facing the first side portion. As a result, a single electrically conductive portion, extending along the outer surface of each of reactors 302 and 304 defines both the shield portion 322 and cathode electrodes 320.

In some configurations, the shield portion 322 can optionally extend around each of reactors 302 and 304. For example, in some configurations, an additional shield portion 324 can be formed on an exterior surface of outer dielectric layer 308. In operation, the additional shield portion 324 can then be coupled to the cathode electrodes 320 and shield portion 322. In another configuration, the additional shield portion 324 for reactors 302 and 304 can be formed by wrapping another foil or sheet around the assembled chambers, i.e., around the outer sides of layers 308 as well as around the sides of the chambers. In such a configuration, the foil defining additional shield portion 324 can be wrapped so as to make electrical contact with electrodes 320 on the sides of the chambers 302 and 304, and thus electrically couple shield portion 322 to shield portion 324.

Such a configuration provides improved performance, in particular as compared to a single reactor system, such as that described in FIGS. 1A and 1B. In particular, where a test reactor was constructed in accordance with FIGS. 3A and 3B and with an additional shield portion 324 for reactors 302 and 304, the present inventor has found that the electrical power consumed in the plasma in such a system was 0.33 W. In contrast, the present inventors have found that electrical power consumed in the plasma was 0.028 W in the case of a device configured in accordance with the single reactor configuration illustrated in FIGS. 1A and 1B and having similar dimensions, a ˜10× increase. The power (P) was calculated by the following formula: P=(∫VI dt)f. The voltage pulse was the same in the two cases, with a peak voltage value of ˜30 kV, and the pulse frequency ˜10 Hz was also the same. Thus, the increase in power is due to corresponding increase in current flowing through the discharge gap during the pulse when the shield portion extends around the discharge chambers.

The coupling between the first and second reactors is reduced or eliminated by providing a shield portion therebetween. However, the various embodiments of the invention are not limited in this regard. As described above, the principal difficulty in generating plasma in two adjacent chambers is the induction of charges on a dielectric surface of a reactor adjacent to another reactor in which plasma is being formed. Accordingly, another embodiment of the invention involves forming plasma in adjacent chambers, without a shield portion therebetween, that fails to induce charges on neighboring dielectric layers. Accordingly, another aspect of the invention provides for plasma formation using a staggered-discharge approach. That is, the adjacent reactors are configured such that the discharge for forming plasma in a first reactor and the discharge for forming plasma in a second, adjacent chamber reactor occur in non-overlapping portions. This is conceptually illustrated with respect to FIG. 4.

FIG. 4 is a partial cross-section diagram of another exemplary configuration for a gas treatment device 400 in accordance with an embodiment of the invention. In particular, FIG. 4 is a stacked arrangement of two of reactor 100 (reactors 100A and 100B), where the cross section shown in FIG. 4 is a portion of the cross-section along cutline 2-2 in FIG. 1 for each of reactors 100A and 100B. Each of reactors 100A and 100B are configured substantially similar to reactor 100 in FIG. 1. Thus, the partial cross-section of device 400 shows the top and bottom dielectric portions 104A and 104B for each of reactors 100A and 100B, respectively, that defines respective ones of discharge chambers 102A and 102B. In device 400, the decoupling between reactors 100 is provided by staggering the portions of each discharge chamber in device 400 that are to be discharged.

This staggering can be provided in several ways. For example, in one configuration, the electrodes 110 and 112 in each discharge chamber 102 can be configured such that when device 200 is assembled, the electrodes that are being biased at the same time do not substantially overlap. For example, as shown in FIG. 4, only the electrodes associated with an upper portion 402 in a first reactor 100 and the electrodes associated with a lower portion 404 in a second reactor 100 are configured to provide a plasma in portions “A” and “B” in device 200. Thus, any charges induced in an adjacent discharge chamber not induced in a portion of the discharge chamber associated with generation of plasma. That is, the charges induced in portion “C” of the second reactor 100 by the plasma in portion “A” of first reactor 100 are inconsequential, since the plasma in second reactor 100 is limited to portion “B”. Similarly, the charges induced in portion “D” of the first reactor 100 by the plasma in portion “B” of second reactor 100 are inconsequential, since the plasma in first reactor 100 is limited to portion “A”. However, in such a configuration, since only a portion of the volume of each discharge chamber is used, the efficiency may be reduced.

In some configurations overlapping portions can be provided by controlling a timing of discharges in device 400. In particular, the timing associated with biasing of the electrodes for these portions can be controlled so that only non-overlapping portions are biased at the same time. Thus, at any one time, only one set of electrodes, associated with non-overlapping portions, are concurrently biased. Such a configuration is advantageous, since switching between the different sets of non-overlapping electrode portions permits a majority of the volume of each discharge chamber 102 in device 400 to be used. Accordingly, a greater efficiency can be achieved.

The gas treatment devices described in FIGS. 2-4 can be incorporated into an exhaust system, as described below with respect to FIG. 5, to provide steam reforming for reducing pollutants in exhaust gases. FIG. 5 is a schematic of an exemplary diesel fuel powered system 500 configured in accordance with an embodiment. For purposes of FIG. 5, some minor components, such as valves, pumps, electrical wiring, and control systems, to name a few, are not shown for ease of illustration.

System 500 includes an engine 502, powered using diesel fuel from a fuel reservoir 504. The system 500 includes an engine air inlet 506 for providing air to engine 502 and an engine exhaust outlet 508 for directing exhaust gas from engine 502. The engine exhaust outlet 508 can be connected to an exhaust system 510 for treating the exhaust gas from engine 502.

Exhaust system 510 can include an inlet portion 512, an outlet portion 514, and a NOx removal reactor 516 therebetween, such as a hydrocarbon selective catalytic reduction (H-SCR) reactor, a NOx adsorbent, or a combination of both. In some configurations, the inlet portion 512 can include a diesel particulate filer (DPF) 518 and an oxidation catalyst 520 to remove particulates, CO, and to oxidize NO to NO₂. Additionally, exhaust system, 510 can include a reforming system 522.

The reforming system 522 can include a water source 524, a diesel fuel source 504, a first heat exchanger 526, a gas treatment device 528, and a recycling system 530. The recycling system 530 can include a treated gas collection line 532 feeding a second heat exchanger 534, which in turns feeds a reactant supply line 536 coupled to the inlet portion 512 and a recycle supply line 538 coupled to the first heat exchanger 526.

System 500 operates as follows. Initially, engine 502 begins to operate. That is fuel from fuel source 504 and air (via air inlet 506) are fed into engine 502 and engine 502 produces exhaust gas at outlet 508. The operation of such engines is well-known to those of ordinary skill in the art and will not be described here. The exhaust gas then propagates through exhaust system 510 for treatment.

First, as described above, the exhaust gas can pass through DPF 518 and oxidation catalyst 520 to remove particulates, CO, and to oxidize NO to NO₂. Second, as the exhaust gas reaches reactor 516, the exhaust gas can be combined with volatile PO—HC and H₂ produced by the reforming system 522 to be utilized in the H-SCR process for reduction of NOx. Further, in the case where a NOx adsorbent is used, the PO—HC and H₂ can be used to regenerate the adsorbent material.

The reforming system 522 operates as follows to produce volatile PO—HC and H₂. First, liquid diesel fuel from fuel source 504 and water from water source 524 is transferred to first heat exchanger 526. In some embodiments, the liquid diesel fuel and the water can be transferring using a fuel pump 540 and a water pump 542, respectively. However, the various embodiments are not limited in this regard and a system relying on gravity can also be used.

Once the liquid diesel fuel and the water reach the first heat exchanger 526, these are vaporized to produce a first gas, consisting of a mixture of vaporized diesel fuel and steam. In the various embodiments, to reduce the power requirements of the reforming system 522, the heat exchanger 526 is in contact with or at least partially disposed in the inlet portion 512. In such a configuration, rather than relying on an external source of heat to vaporize the liquid diesel fuel and water, the heat present in the exhaust gas (typically >100° C.) is utilized to introduce the necessary heat for causing vaporization. In some embodiments, the first heat exchanger 526 can be contained entirely within inlet portion 512.

The first gas can then be directed into gas treatment device 528. The gas treatment device can be configured in accordance with any of the configurations in FIGS. 1-4. However, the configuration in FIGS. 2-4 will generally provide a more efficient and compact arrangement for gas treatment device 528. Operation of gas treatment device 528 results in at least some of the hydrocarbons in the vaporize diesel fuel to be converted to volatile PO—HC and H₂, thus resulting in a second gas to be formed that includes the volatile PO—HC and H₂, as well as any non-reacted vaporized diesel fuel and steam. In the various embodiments, to further reduce the power requirements of the reforming system 522, the gas treatment system 528 can also be in contact with or at least partially disposed in the inlet portion 512. In such a configuration, an external source of heat would not be required to maintain the liquid diesel fuel and water and water in a vaporized state, as the heat present in the exhaust gas (typically >100° C.) is utilized to introduce the necessary heat for maintaining vaporization. In some embodiments, the gas treatment system 528 can be contained entirely within inlet portion 512.

The second gas, produced by gas treatment device 528, can then be directed from gas treatment device 528 to the second heat exchanger 534 in recycling system 530 via gas collection line 532. The second gas is then cooled in second heat exchanger 534 using air or any other gas to reduce the temperature of the second gas below 100° C. and cause condensation of at least a portion of the diesel fuel and steam remaining in the second gas. As a result, a third gas, primarily volatile PO—HC and H₂ and a liquid mixture of diesel fuel and water are produced. The liquid mixture can be redirected into the first heat exchanger 526 via recycle supply line 538, where it can be re-vaporized and subsequently retreated using gas treatment device 528. The third gas can be concurrently redirected into inlet portion 512, to combine with the exhaust gas prior to reactor 516.

The system and method described above is particularly advantageous because it utilizes existing infrastructure, i.e., fuel tank 504 for providing fuel to engine 502, surplus heat of the exhaust gas to vaporize the liquid diesel fuel and water, and electrical power required for the gas treatment device 528 can be generated by an alternator or other electrical power generating device already present in the system.

Further, the system and method described above are different from previously available systems in various ways. For example, conventional catalytic steam reforming of fuel generally requires the heating of gases to higher temperatures than possible with the configuration or materials that would be used for the system of FIG. 5. That is, temperatures in the range of 3000K to 10,000K are typically required for steam reforming, which normally result in heat losses and material compatibility issues. In contrast, stream reforming in accordance with the various embodiments can be performed at the significant lower temperatures associated with vehicle engine exhaust, typically less than 500K. Further, such systems generally suffer from frequent catalyst deactivation. In contrast, the plasma processes possible for the gas treatment devices of FIGS. 1-4 can tolerate the impurities that are responsible for the catalyst deactivation. Additionally, even in systems where partial oxidation of diesel fuel is performed using plasma reactor, several major drawbacks have been reported. First, fire hazard limits the allowed concentration of fuel to be very low. That is, the lower explosive or flammable limits for gasoline and kerosene are 1.4% and 0.7% concentrations, respectively. Thus, if the concentration of these fuels in air is higher than these values, the likelihood of an explosion is high. Second, the amount of hydrogen in the product gases resulting from such processes is relatively low because a fraction of it is consumed by surplus oxygen by following reactions: partial oxidation C_(n)H_(m)+(n/2)O₂→nCO+(m/2)H₂, water formation 2H₂+O₂→2H₂O. Finally, cock or wax deposition on electrodes typically poses a problem in these processes.

In contrast, configurations in accordance with the various embodiments provide steam reforming that allows higher concentrations of hydrocarbons to be treated without fire hazard and without cock or wax deposition on electrodes. For example, the inclusion of steam allows for concentrations up to 20%. Further, such steam reforming yields more hydrogen from water vapors in addition to the hydrogen coming from hydrocarbons by reactions such as the following: C_(n)H_(m)+nH₂O→nCO+(n+(m/2))H₂, and 2H₂O+CO→H₂+CO₂.

Additionally, the systems and methods described above provide additional advantages. For example, although steam reforming of light hydrocarbons, i.e., methane, propane, and hexane can be performed using non-thermal plasmas, in the diesel engine setup, additional fuel tanks and related infrastructure would be required. Further, such processes are generally limited to gaseous fuels or require dilution of the process gas with some inert gas, increasing overall complexity of the system. Also, the non-thermal plasmas typically reported for reforming light hydrocarbons are generally inefficient compared with the surface-plasma of this embodiment.

The present configuration also produces plasma in gas phase which is different from arc discharges directly in liquid fuels. Such arc discharges in liquids are close to thermal plasma, where energy wastage as heat loses is a problem. Further, such discharges also generally result in cracking of diesel fuel that produces many solid carbon particles and light hydrocarbons along with hydrogen. The solid carbon needs to be filtered out continually from the fuel as they are electrically conductive particles that interfere with the plasma process. Further, PO—HC is not produced in this process as there is no source of oxygen in the system. As a result additional filtering and processing would be needed, as compared to the system and methods described above.

FIG. 6 illustrating a system including a gas treatment device 602, configured in accordance with an embodiment of the invention, and supporting electrical circuitry. In operation, a high voltage pulse can be applied to device 602. In the various embodiments, the pulse can be formed using a capacitive discharge circuit or an inductive discharge circuit. In the case of a capacitive discharge circuit, the pulse forming element can be single or multiple capacitors 656, where one of them could be used to change the polarity of the pulse. It can also be combinations of capacitors and inductors, which form a pulse forming circuit, or cables and other pulse forming lines. In the case of an inductive discharge circuit, the pulse forming element can be an inductor or a combination of inductors and capacitors, which form a pulse forming circuit, or combinations thereof. The capacitive storage elements are charged by a power supply 650, either through a resistor 655 or in a pulsed mode through an inductor. In the case of capacitive discharges, the switch must be a closing switch, e.g. a spark gap switch 625 or any other high power closing switch. The switch should be preferably controllable, e.g. triggereable with a trigger generator 651. In case of a an inductive storage system, the switch needs to be an opening switch. The circuit also contains resistors which are placed in parallel 655 or in series to the load, the reactor 602. The pulse is generated by closing the switch 625, or in the case of an inductive circuit, opening a switch. This pulse was applied to high voltage electrode node 657 (i.e., the anode electrode), while counter electrode node 658 (i.e., the cathode electrode and/or shield portions) was grounded (i.e., coupled to ground node 653). A control system 660 can be provided to monitor and control the various elements in system 600. Other components can also be provided, such as resistor 654 for providing a voltage divider for measuring voltage. The pulse duration preferably is short enough to prevent the occurrence of a transition from streamer to arc. Those skilled in the art will readily see that a variety of circuits may be used and pulses having different characteristics may readily be achieved.

Referring now to FIG. 7, there is provided a detailed block diagram of a computing device 700 which can be implemented as control system 660. Although various components are shown in FIG. 7, the computing device 700 may include more or less components than those shown in FIG. 7. However, the components shown are sufficient to disclose an illustrative embodiment of the invention. The hardware architecture of FIG. 7 represents only one embodiment of a representative computing device for controlling a jointed mechanical device.

As shown in FIG. 7, computing device 700 includes a system interface 722, a Central Processing Unit (CPU) 706, a system bus 710, a memory 716 connected to and accessible by other portions of computing device 700 through system bus 710, and hardware entities 714 connected to system bus 710. At least some of the hardware entities 714 perform actions involving access to and use of memory 716, which may be any type of volatile or non-volatile memory devices. Such memory can include, for example, magnetic, optical, or semiconductor based memory devices. However the various embodiments of the invention are not limited in this regard.

In some embodiments, computing system can include a user interface 702. User interface 702 can be an internal or external component of computing device 700. User interface 702 can include input devices, output devices, and software routines configured to allow a user to interact with and control software applications installed on the computing device 700. Such input and output devices include, but are not limited to, a display screen 704, a speaker (not shown), a keypad (not shown), a directional pad (not shown), a directional knob (not shown), and a microphone (not shown). As such, user interface 702 can facilitate a user-software interaction for launching software development applications and other types of applications installed on the computing device 700.

System interface 722 allows the computing device 700 to communicate directly or indirectly with the other devices, such as an external user interface or other computing devices. Additionally, computing device can include hardware entities 714, such as microprocessors, application specific integrated circuits (ASICs), and other hardware. As shown in FIG. 7, the hardware entities 714 can also include a removable memory unit 716 comprising a computer-readable storage medium 718 on which is stored one or more sets of instructions 720 (e.g., software code) configured to implement one or more of the methodologies, procedures, or functions described herein. The instructions 720 can also reside, completely or at least partially, within the memory 716 and/or within the CPU 706 during execution thereof by the computing device 700. The memory 716 and the CPU 706 also can constitute machine-readable media.

While the computer-readable storage medium 718 is shown in an exemplary embodiment to be a single storage medium, the term “computer-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “computer-readable storage medium” shall also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present disclosure.

The term “computer-readable storage medium” shall accordingly be taken to include, but not be limited to solid-state memories (such as a memory card or other package that houses one or more read-only (non-volatile) memories, random access memories, or other re-writable (volatile) memories), magneto-optical or optical medium (such as a disk or tape). Accordingly, the disclosure is considered to include any one or more of a computer-readable storage medium or a distribution medium, as listed herein and to include recognized equivalents and successor media, in which the software implementations herein are stored.

System interface 722 can include a network interface unit configured to facilitate communications over a communications network with one or more external devices. Accordingly, a network interface unit can be provided for use with various communication protocols including the IP protocol. Network interface unit can include, but is not limited to, a transceiver, a transceiving device, and a network interface card (NIC).

As noted above, those skilled in the art will recognize that such a plasma reactor may not only be used with conventional gas treatment, but also for decontamination, odor control, etc. While the description above refers to particular embodiments of the invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the invention.

For example, although the various embodiments have been discussed above with respect to hydrocarbons, the methods described herein are equally application to removing other types of contaminants from air and other gases. One potential use of the systems and methods of the various embodiments is for the reduction of sulfur contents from liquid fossil fuels is important for production of good quality environment friendly fuels. Accordingly, the systems and methods of the various embodiments can be used in hydro-desulfurization by employing hydrogen and suitable catalysts to break carbon-sulfur bond in the sulfur containing compounds and make hydrogen-sulfur bonds to convert sulfur into gaseous hydrogen sulfide. The systems and methods of the various embodiments can also be used for oxidative desulfurization to provide an alternate technique to oxidize the sulfur compounds into higher oxidation states, like sulfones or sulfoxides which can be extracted from the fuels. A non-thermal plasma based technique can be used as a source of oxidizing agents for oxidative desulfurization.

Previous experiments with plasma reactors in which the insulating walls were designed to confine the plasma in narrower spaces, showed that the efficiency of these sliding discharges for oxidation of organic compounds in air can be increased by more than 500% as illustrated in FIG. 8. FIG. 8 is a bar chart showing a comparison of energy cost for partial oxidation of organic pollutants from air and reduction of nitric oxide from nitrogen in pulsed corona discharges in air (conventional plasma reactors) and the sliding discharge reactor.

As noted above, introduction of a shield around the discharge chamber allows increasing the energy density in the plasma, shown in FIG. 8 to be about forty times, without loss of efficiency for the chemical reactions that makes the plasma reactor compact and scalable for high throughput relevant to commercial applications. The reasons for these dramatic improvements in energy deposition and efficiency are assumed to be due to: i) the increased interaction of the sliding discharges with the solid surfaces that supplies additional free electrons through bombardment of charged particles on the surface or thermionic/photo emissions and ii) adsorption and stabilization of short lived active species on the surfaces that otherwise would be destroyed in the gas phase. A similar improvement in efficiency can be provided in oxidation of sulfur compounds.

For such processes, the sliding discharges of the various embodiments can operate in air as well as in presence of any proportion of water vapors in the process gas. The plasma in water vapors (steam) simultaneously produces reducing agents and oxidizing agents. These agents can be utilized to reduce and/or oxidize organic compounds. Oxidation of benzene a representative organic compound has already been demonstrated and desulfurization in accordance with the various embodiments would occur in a similar fashion, by simultaneously oxidizing a fraction of sulfur compounds and reduction of the remaining fraction from fossil fuels.

The systems and methods of the various embodiments can also be used to provide a plasma device that operates as an air filter for destroying any air borne toxic chemical, bacterial or viral agent. In order to obtain breathable air, it is desirable to mitigate unwanted by-products of plasma, such as ozone and nitrogen oxides. This can be achieved by employing suitable catalysts in the plasma device. For example, some crystalline forms of aluminum oxide can enhance ozone while some other crystalline forms of the same material can destroy ozone in the plasma device. Since the plasma device of the various embodiments is compact and easily scalable by stacking and operating multiple discharge chambers in parallel, it can be utilized to form an air filter for destroying air borne toxic chemical, bacterial or viral agent.

In the case of the proposed shielded sliding discharge device of the various embodiments, the dielectric surface in contact with the plasma can itself act as a catalyst or a suitable catalyst can be deposited on the dielectric surface. A layer of porous ceramic layer can be deposited on the dielectric to provide large area catalyst support for this purpose. This combination of compact plasma device and catalyst can potentially be developed as a device for protection against chemical and biological warfare agents.

Applicants present certain theoretical aspects above that are believed to be accurate that appear to explain observations made regarding embodiments of the invention. However, embodiments of the invention may be practiced without the theoretical aspects presented. Moreover, the theoretical aspects are presented with the understanding that Applicants do not seek to be bound by the theory presented.

While various embodiments of the invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.

Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 

What is claimed is:
 1. A method for treatment of a heated exhaust gas comprising hydrocarbons, the method comprising: providing a first gas comprising a gaseous mixture of vaporized diesel fuel and steam; treating the first gas using at least one corona discharge comprising a combination of streamers to transform the first gas into a second gas comprising volatile partially oxidized hydrocarbons (PO—HC) and hydrogen gas (H₂), the combination of streamers comprising primarily surface streamers; extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas; directing a combination of the third gas and the exhaust gas into a nitrogen oxides (NOx) reduction reactor.
 2. The method of claim 1, wherein the step of providing further comprises: directing a liquid mixture of liquid diesel fuel and water into a heat exchanger; and applying the heated exhaust gas to the heat exchanger to vaporize the liquid mixture and produce the first gas.
 3. The method of claim 1, wherein the step of treating further comprises: providing one or more discharge chambers defined by a plurality of dielectric sections, each of the discharge chambers comprising at one or more sets of first and second electrodes for producing electric fields in the discharge chambers, the plurality of dielectric sections and the sets of first and second electrodes arranged to define a volume in each of the discharge chambers that inhibits the formation of volume-streamers, and the discharge chambers being configured to prevent pulsed electric fields generated in adjacent ones of the discharge chambers from substantially interacting; directing the first gas into the discharge chambers; generating the corona discharge in the discharge chambers using a pulsed electric field generated by each of the sets of the first and second electrodes in the discharge chambers; and releasing the second gas from the discharge chambers.
 4. The method of claim 3, further comprising heating the discharge chambers using the heated exhaust gas.
 5. The method of claim 1, wherein the step of extracting further comprises: directing the second gas into a heat exchanger; cooling the second gas in the heat exchanger to condense water and liquid diesel fuel from the second gas.
 6. The method of claim 5, wherein the step of providing further comprises: forming at least a portion of the first gas using the condensed water and the condensed liquid diesel fuel.
 7. An exhaust system, comprising: a nitrogen oxides (NOx) removal reactor; an inlet portion configured for receiving a heated exhaust gas comprising hydrocarbons and directing the heated exhaust gas into the catalytic reactor; and a reformer system heated by the heater exhaust gas, the reformer system comprising: a gas treatment device for treating a first gas comprising a mixture of vaporized diesel fuel and steam using at least one corona discharge comprising a combination of streamers to transform the first gas into a second gas comprising volatile partially oxidized hydrocarbons (PO—HC) and hydrogen (H₂), the combination of streamers comprising primarily surface streamers, and a recycling system for extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas and directing the third gas into the inlet portion.
 8. The system of claim 7, wherein the reformer system further comprises a first heat exchanger for receiving a liquid mixture of liquid diesel fuel and water and generating the first gas, wherein the first heat exchanger is configured for generating the first gas by vaporizing the liquid mixture using the heated exhaust gas.
 9. The system of claim 8, wherein the heat exchanger is disposed in the inlet portion.
 10. The system of claim 8, wherein the recycling system comprises: a second heat exchanger coupled to an outlet of the plasma reactor and configured for producing the third gas by condensing water and liquid diesel fuel from the second gas; a recycle supply line for directing the condensed water and the condensed liquid diesel fuel from the second heat exchanger to the first heat exchanger; and a reactant supply line for directing the third gas from the second heat exchanger to the inlet portion.
 11. The system of claim 8, further comprising: a water source for providing the water to the first heat exchanger; and a fuel source for providing the liquid diesel fuel to the first heat exchanger.
 12. The system of claim 1, wherein the gas treatment device comprises one or more discharge chambers defined by a plurality of dielectric sections, each of the discharge chambers comprising at one or more sets of first and second electrodes for producing electric fields in the discharge chambers, wherein the plurality of dielectric sections and the sets of first and second electrodes are arranged to define a volume in each of the discharge chambers that inhibits the formation of volume-streamers, and wherein the discharge chambers being configured to prevent pulsed electric fields generated in adjacent ones of the discharge chambers from substantially interacting.
 13. The system of claim 12, further comprising heating the discharge chambers using the heated exhaust gas.
 14. The system of claim 12, wherein the discharge chambers are disposed in the inlet portion.
 15. The system of claim 12, wherein the NOx removal reactor comprises at least one of a hydrocarbon selective catalytic reduction (H-SCR) reactor and a NOx adsorbent.
 16. A diesel fuel powered system, comprising: a diesel fuel engine comprising an exhaust outlet for releasing exhaust gas; a hydrocarbon selective catalytic reduction (H-SCR) reactor; an inlet portion configured for directing the exhaust gas from the exhaust outlet to the H-SCR reactor; a gas treatment device at least partially disposed in the inlet portion, the gas treatment device configured for treating a first gas comprising a mixture of vaporized diesel fuel and steam using at least one corona discharge comprising a combination of streamers to transform the first gas into a second gas comprising volatile partially oxidized hydrocarbons (PO—HC) and hydrogen (H₂), the combination of streamers comprising primarily surface streamers, a first heat exchanger at least partially disposed in the inlet portion and configured for generating the first gas from water and liquid diesel fuel using a heat of the exhaust outlet; a recycling system coupled to the plasma reactor to receive the second gas, the recycling system configured for extracting liquid diesel fuel and water from the second gas to form a third gas, directing the third gas into the inlet portion, and directing the extracted liquid diesel fuel and the extracted water into the first heat exchanger.
 17. The system of claim 16, wherein the recycling system comprises: a second heat exchanger coupled to an outlet of the plasma reactor and configured for producing the third gas by condensing water and liquid diesel fuel from the second gas; a recycle supply line for directing the condensed water and the condensed liquid diesel fuel from the second heat exchanger to the first heat exchanger; and a reactant supply line for directing the third gas from the second heat exchanger to the inlet portion.
 18. The system of claim 16, further comprising: a water source for providing the water to the first heat exchanger; and a fuel source for providing the liquid diesel fuel to the first heat exchanger and the diesel fuel engine.
 19. The system of claim 16, wherein the gas treatment device comprises one or more discharge chambers defined by a plurality of dielectric sections, each of the discharge chambers comprising at one or more sets of first and second electrodes for producing electric fields in the discharge chambers, wherein the plurality of dielectric sections and the sets of first and second electrodes are arranged to define a volume in each of the discharge chambers that inhibits the formation of volume-streamers, and wherein the discharge chambers being configured to prevent pulsed electric fields generated in adjacent ones of the discharge chambers from substantially interacting.
 20. The system of claim 19, wherein the discharge chambers are disposed in the inlet portion.
 21. The system of claim 16, wherein the first heat exchanger is disposed in the inlet portion.
 22. An exhaust system, comprising: a nitrogen oxides (NOx) removal reactor; an inlet portion configured for receiving a heated exhaust gas comprising hydrocarbons and directing the heated exhaust gas into the catalytic reactor; and a reformer system heated by the heater exhaust gas in the inlet portion, the reformer system comprising a plasma reactor for treating a first gas comprising a mixture of vaporized diesel fuel and steam using at least one corona discharge comprising volume streamer and surface streamers to transform the first gas into a second gas comprising volatile partially oxidized hydrocarbons (PO—HC) and hydrogen (H₂), and a recycling system for extracting at least a portion of vaporized diesel fuel and steam from the second gas to form a third gas and for directing the third gas into the inlet portion, wherein the plasma reactor comprises a plurality of dielectric sections defining two or more discharge chambers for treating the first gas, first and second electrodes disposed in each of the discharge chambers, and electrically conductive shield portions positioned between adjacent ones of the discharge chambers, and wherein the plurality of dielectric sections and the first and second electrodes are arranged so that a greater portion of overall energy density within the discharge chambers is due to the surface-streamers. 